.\"	$OpenBSD: hexdump.1,v 1.25 2014/11/15 14:41:02 bentley Exp $
.\"	$NetBSD: hexdump.1,v 1.14 2001/12/07 14:46:24 bjh21 Exp $
.\"
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.\"	from: @(#)hexdump.1	8.2 (Berkeley) 4/18/94
.\"
.Dd $Mdocdate: November 15 2014 $
.Dt HEXDUMP 1
.Os
.Sh NAME
.Nm hexdump
.Nd ascii, decimal, hexadecimal, octal dump
.Sh SYNOPSIS
.Nm hexdump
.Bk -words
.Op Fl bCcdovx
.Op Fl e Ar format_string
.Op Fl f Ar format_file
.Op Fl n Ar length
.Op Fl s Ar offset
.Op Ar
.Ek
.Sh DESCRIPTION
The
.Nm
utility is a filter which displays the specified files, or
the standard input, if no files are specified, in a user-specified
format.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl b
.Em One-byte octal display .
Display the input offset in hexadecimal, followed by sixteen
space-separated, three column, zero-filled, bytes of input data,
in octal, per line.
.It Fl C
.Em Canonical hex+ASCII display .
Display the input offset in hexadecimal, followed by sixteen
space-separated, two column, hexadecimal bytes, followed by the
same sixteen bytes in %_p format enclosed in
.Sq |
characters.
.It Fl c
.Em One-byte character display .
Display the input offset in hexadecimal, followed by sixteen
space-separated, three column, space-filled, characters of input
data per line.
.It Fl d
.Em Two-byte decimal display .
Display the input offset in hexadecimal, followed by eight
space-separated, five column, zero-filled, two-byte units
of input data, in unsigned decimal, per line.
.It Fl e Ar format_string
Specify a format string to be used for displaying data.
.It Fl f Ar format_file
Specify a file that contains one or more newline separated format strings.
Empty lines and lines whose first non-blank character is a hash mark
.Pq Ql #
are ignored.
.It Fl n Ar length
Interpret only
.Ar length
bytes of input.
By default,
.Ar length
is interpreted as a decimal number.
With a leading
.Cm 0x
or
.Cm 0X ,
.Ar length
is interpreted as a hexadecimal number,
otherwise, with a leading
.Cm 0 ,
.Ar length
is interpreted as an octal number.
.It Fl o
.Em Two-byte octal display .
Display the input offset in hexadecimal, followed by eight
space-separated, six column, zero-filled, two byte quantities of
input data, in octal, per line.
.It Fl s Ar offset
Skip
.Ar offset
bytes from the beginning of the input.
By default,
.Ar offset
is interpreted as a decimal number.
With a leading
.Cm 0x
or
.Cm 0X ,
.Ar offset
is interpreted as a hexadecimal number,
otherwise, with a leading
.Cm 0 ,
.Ar offset
is interpreted as an octal number.
Appending the character
.Cm b ,
.Cm k ,
or
.Cm m
to
.Ar offset
causes it to be interpreted as a multiple of
.Li 512 ,
.Li 1024 ,
or
.Li 1048576 ,
respectively.
.It Fl v
The
.Fl v
option causes hexdump to display all input data.
Without the
.Fl v
option, any number of groups of output lines, which would be
identical to the immediately preceding group of output lines (except
for the input offsets), are replaced with a line comprised of a
single asterisk
.Pq Ql * .
.It Fl x
.Em Two-byte hexadecimal display .
Display the input offset in hexadecimal, followed by eight, space
separated, four column, zero-filled, two-byte quantities of input
data, in hexadecimal, per line.
.El
.Pp
For each input file,
.Nm
sequentially copies the input to standard output, transforming the
data according to the format strings specified by the
.Fl e
and
.Fl f
options, in the order that they were specified.
.Ss Formats
A format string contains any number of format units, separated by
whitespace.
A format unit contains up to three items: an iteration count, a byte
count, and a format.
.Pp
The iteration count is an optional positive integer, which defaults to
one.
Each format is applied iteration count times.
.Pp
The byte count is an optional positive integer.
If specified it defines the number of bytes to be interpreted by
each iteration of the format.
.Pp
If an iteration count and/or a byte count is specified, a single slash
.Pq Sq /
must be placed after the iteration count and/or before the byte count
to disambiguate them.
Any whitespace before or after the slash is ignored.
.Pp
The format is required and must be surrounded by double quote
.Pq \&"\& \&"
marks
(the quote mark is a special character in many shell programs,
and may have to be escaped from the shell).
It is interpreted as a fprintf-style format string (see
.Xr fprintf 3 ) ,
with the
following exceptions:
.Bl -bullet -offset indent
.It
An asterisk (*) may not be used as a field width or precision.
.It
A byte count or field precision
.Em is
required for each
.Sq s
conversion character (unlike the
.Xr fprintf 3
default which prints the entire string if the precision is unspecified).
.It
The conversion characters
.Sq h ,
.Sq l ,
.Sq n ,
.Sq p ,
and
.Sq q
are not supported.
.It
The single character escape sequences
described in the C standard are supported:
.Pp
.Bl -tag -width "Xalert characterXXX" -offset indent -compact
.It NUL
\e0
.It Aq alert character
\ea
.It Aq backspace
\eb
.It Aq form-feed
\ef
.It Aq newline
\en
.It Aq carriage return
\er
.It Aq tab
\et
.It Aq vertical tab
\ev
.El
.El
.Pp
.Nm
also supports the following additional conversion strings:
.Bl -tag -width Fl
.It Cm \&_a Ns Op Cm dox
Display the input offset, cumulative across input files, of the
next byte to be displayed.
The appended characters
.Cm d ,
.Cm o ,
and
.Cm x
specify the display base
as decimal, octal or hexadecimal respectively.
.It Cm \&_A Ns Op Cm dox
Identical to the
.Cm \&_a
conversion string except that it is only performed
once, when all of the input data has been processed.
.It Cm \&_c
Output characters in the default character set.
Nonprinting characters are displayed in three character, zero-padded
octal, except for those representable by standard escape notation
(see above),
which are displayed as two character strings.
.It Cm _p
Output characters in the default character set.
Nonprinting characters are displayed as a single dot
.Ql \&. .
.It Cm _u
Output US ASCII characters, with the exception that control characters are
displayed using the following, lower-case, names.
Other non-printable characters are displayed as hexadecimal strings.
.Bd -literal -offset 3n
000 nul  001 soh  002 stx  003 etx  004 eot  005 enq
006 ack  007 bel  008 bs   009 ht   00A lf   00B vt
00C ff   00D cr   00E so   00F si   010 dle  011 dc1
012 dc2  013 dc3  014 dc4  015 nak  016 syn  017 etb
018 can  019 em   01A sub  01B esc  01C fs   01D gs
01E rs   01F us   07F del
.Ed
.El
.Pp
The default and supported byte counts for the conversion characters
are as follows:
.Bl -tag -width  "Xc,_Xc,_Xc,_Xc,_Xc,_Xc" -offset indent
.It Li \&%_c , \&%_p , \&%_u , \&%c
One byte counts only.
.It Xo
.Li \&%d , \&%i , \&%o ,
.Li \&%u , \&%X , \&%x
.Xc
Four byte default, one, two, four and eight byte counts supported.
.It Xo
.Li \&%E , \&%e , \&%f ,
.Li \&%G , \&%g
.Xc
Eight byte default, four byte counts supported.
.El
.Pp
The amount of data interpreted by each format string is the sum of the
data required by each format unit, which is the iteration count times the
byte count, or the iteration count times the number of bytes required by
the format if the byte count is not specified.
.Pp
The input is manipulated in
.Dq blocks ,
where a block is defined as the
largest amount of data specified by any format string.
Format strings interpreting less than an input block's worth of data,
whose last format unit both interprets some number of bytes and does
not have a specified iteration count, have the iteration count
incremented until the entire input block has been processed or there
is not enough data remaining in the block to satisfy the format string.
.Pp
If, either as a result of user specification or hexdump modifying
the iteration count as described above, an iteration count is
greater than one, no trailing whitespace characters are output
during the last iteration.
.Pp
It is an error to specify a byte count as well as multiple conversion
characters or strings unless all but one of the conversion characters
or strings is
.Cm \&_a
or
.Cm \&_A .
.Pp
If, as a result of the specification of the
.Fl n
option or end-of-file being reached, input data only partially
satisfies a format string, the input block is zero-padded sufficiently
to display all available data (i.e., any format units overlapping the
end of data will display some number of the zero bytes).
.Pp
Further output by such format strings is replaced by an equivalent
number of spaces.
An equivalent number of spaces is defined as the number of spaces
output by an
.Cm s
conversion character with the same field width
and precision as the original conversion character or conversion
string but with any
.Ql + ,
.Ql \&\ \& ,
.Ql #
conversion flag characters
removed, and referencing a NULL string.
.Pp
If no format strings are specified, the default display is equivalent
to specifying the
.Fl x
option.
.Sh EXIT STATUS
.Ex -std hexdump
.Sh EXAMPLES
Display characters using a fieldwidth of 4,
and using special names for control characters:
.Pp
.Dl $ hexdump -e '"%4_u"' file
.Pp
An example file for use with the
.Fl f
option, to display the input in perusal format:
.Bd -literal -offset indent
"%06.6_ao "  12/1 "%3_u "
"\et\et" "%_p "
"\en"
.Ed
.Pp
An example file for use with the
.Fl f
option, which implements the equivalent of the
.Fl x
option:
.Bd -literal -offset indent
"%07.7_Ax\en"
"%07.7_ax " 8/2 "   %04x " "\en"
.Ed
.Sh SEE ALSO
.Xr od 1
